1. Field of the Invention
The invention relates to a process of attaching insulation pads to automotive floor coverings using a thermoplastic fastener.
2. Description of the Prior Art
The present invention relates to floor carpets such as those used in the passenger compartments or luggage compartments of automobiles, and in particular, it relates to means for attaching underpads to the backings of the floor carpets.
Floor coverings that are found in automobiles generally are made with a carpeted face surface and backed with a pliable thermoplastic material such as polyethylene, polypropylene, and ethylene vinyl acetate. The automotive trucks and vans also use floor coverings made of thermoplastic materials such as vinyls or thermoplastic olefins. Attached to that pliable thermoplastic backing generally is a fiber or foam insulation material which makes the vehicle quieter and more comfortable, and cuts down on noise and heat transfer into the interior of the automobile. These insulation pads can either be flat, or molded in a three-dimensional shape as desired.
Presently there are at least two ways presently used to attach the insulating pads to the floor coverings.
A first method is to place the insulation pad into the bottom half of the carpet molding tool and actually mold the carpet onto the pad. The pad will bond to the carpet backing provided the thermoplastic carpet backing was heated to a high enough temperature to reach its softening point and become sticky. A problem with this procedure is that problems occur in cooling the thermoplastic carpet backing when it is in the mold. There is no easy way to remove the heat from the carpet backing because the pad acts as an insulator between the chilled molding surface and the hot thermoplastic carpet backing. The carpet backing must be cooled before removing from the mold to maintain its molded shape, and the result is a much longer cycle time in the mold than is desired.
A second method of attaching the underpad to the carpet backing is to bond it with an adhesive after the carpet has been molded. This method of attachment requires very short cooling cycles because the thermoplastic carpet backing will be in direct contact with the cool molding tool. Draw-backs to this method are the cost of the adhesive, additional labor costs of gluing and the environmental issues. Special adhesives that will pass the automotive performance specifications are required which limits the choices. Finally, adhesive also has to be compatible with the carpet backing and the type of the pad being used, requiring various types of adhesives or various backing and pad constructions. Solvent based adhesives create the environmental problems, requiring pollution control and health hazards for the operators. Cleaning of equipment used for handling of the adhesives, disposal of excessive adhesive etc. produce additional environmental problems.
The automotive industry is striving towards "green cars," which are designed for disassembly, such that after the vehicles of the future have reached the end of their life cycle, the vehicles can be stripped and disassembled and its components can be recycled back in to other automotive parts. Bonding the insulation pads to the floor covering either in the mold or by adhesives, makes it very difficult to separate the two components for recycling.